Galaxy Clusters Have Been Surrounded by High-Energy Particles for Almost Their Entire History

If you could see the Universe through a radio-wave “eye”, you’d detect mini-halos of relativistic particles creating radio emissions around some galaxy clusters. Astronomers long figured those halos are relative “recent” happenings in the nearby Universe and didn’t occur in the early epochs of cosmic history. That’s all changed now that the Low Frequency Array (LOFAR) radio observatory in Europe has revealed newborn galaxies in the early Universe already surrounded by a halo of particles. It’s a rare look at what such clusters were like soon after they formed.